It's not easy for Black to protect the b7-pawn. The problem is that b7-b6 is tactically refuted due to the loose placement of the bishop on d7.
9... c4c3 Before giving the pawn back, Black spoils White's pawn structure a little bit. All this is already well-established by opening theory. 10. b2c3  10... e8g8  11. f3e1 An interesting move, much less played than 11.Nb3. 11... c8d7 Arjun was probably surprised by White's last move since he responded with an inaccuracy. It's important to keep the pawn on b7 defended for now. Both 11...Rd8 and 11...Be7 are better.